Percutaneous transluminal coronary angioplasty (PTCA) and intravascular stenting are among the primary methods of choice to treat coronary artery disease (CAD). Limitations of long-term success include abrupt closure and restenosis, or chronic reclosure, of the vessel - both of which are associated with excessive vascular injury. Intravascular stenting has demonstrated moderate success in addressing these issues. However, current stents tend to be highly thrombogenic and immunologically stimulating. In this Phase I project we propose the novel application of a photochemically activated 1.8-naphthalimide dye in vascular repair following PTCA administration. By utilizing arterial wall and plaque proteins we may be able to produce an "endogenous" stent. Introduction and activation of the dye during a final balloon dilatation would cross-link the proteins in the dilated state and repair intimal or medial dissections resulting from the PTCA administration. In doing so, we may provide short- term structural support during the critical post-angioplasty period, as well as a physical barrier limiting exposure of subendothelium to circulating blood and vasoactive factors associated with the restenosis process. Initial results with these dyes in other tissues have yielded outstanding histological results with minimal cellular proliferation or extracellular matrix deposition and no inflammatory response. Phase II research will involve in vivo animal testing of the proposed "endogenous" stent with human testing and commercialization occurring in Phase III. PROPOSED COMMERCIAL APPLICATION: Over 500,000 balloon angioplasties will be performed in the world this year. This technique, utilizing the dye and a fiber-optic based catheter system to create an 'endogenous" stent, could potentially be used in each of these cases. At current rates, as many as 250,000 may need repeat procedures. A drop in post-PTCA restenosis from 330% to 250% would save approximately S750 million.